Nucleotide substitution: G?A.
Point mutation (AG to AA) in the splice acceptor site of the final (third) intron. This results in the use of a cryptic downstream splice acceptor site within the third exon, producing a transcript which contains a 30bp deletion relative to wild type and a protein with a 10 amino acid internal deletion within the T-box domain.
G5465893A
AG to AA mutation in splice acceptor for final intron results in the use of a cryptic splice acceptor downstream and the loss of 10 amino acids from the beginning of exon 4.
gonad | embryonic stage (with mid1)
gonad | embryonic stage (with mid2)
midB23 mutants exhibit defects in embryonic germ cell migration. Although the mutant embryos show wild type early germ cell migration and the germ cells move into the mesoderm normally at stage 11, by stage 13 the germ cells do not align in a row and instead appear scattered. Similar defects are seen in midB23/Df(2L)Exel6012 transheterozygotes. Somatic gonadal precursor (SGP) specification and contact formation occur normally in midB23 mutant embryos, but the fusion of the three SGP clusters that occurs in wild type does not always take place, with one cluster (typically, but not necessarily the anterior) disjoined from the other two clusters. Unlike in wild type, many germ cells in stage 13 embryos are scattered in the vicinity of the gonad and are not always associated with the SGPs. These mutant gonads fail to coalesce into the tight, round gonad seen in wild type. The SGP clusters that are occupied with germ cells remain elongated into the later stages of gonad development. midB23 mutant SGPs lack the actin-rich protrusions seen in controls.
midB23/mid1 mutant embryos exhibit gonad development defects that are similar in penetrance and severity to midB23 homozygotes.
midB23/mid2 mutant embryos exhibit gonad development defects that are similar in penetrance and severity to midB23 homozygotes.
Homozygous midB23 mutant embryos display severe interruptions in the longitudinal axonal tracts of the ventral nerve cord.
midB23/mid1 is partially rescued by Scer\GAL4twi.PG/midUAS.cBa
midB23/mid1 is partially rescued by Scer\GAL4Six4.PT/midUAS.cBa
Expression of midScer\UAS.cBa in the mesoderm under the control of Scer\GAL4twi.PG fully rescues the lack of somatic gonadal precursor (SGP) cluster fusion and germ cell ensheathment seen in midB23/mid1 mutant embryos. The number of scattered germ cells is reduced. The SGP-related defects are also rescued in the majority of embryos when midScer\UAS.cBa is expressed under the control of Scer\GAL4Six4.PT, but not to the extent seen with Scer\GAL4twi.PG.
This allele was generated in the EMS screen described in Barbosa et al., 2007 (FBrf0200974).